1. Field of the Invention
This invention relates to paperboard laminates for pharmaceutical blister packaging. Such structures of this type, generally, employ a hot melt adhesive and calcium carbonate (CaCO.sub.3) blend which is capable of sealing to polytrichlorofluoroethylene (Aclar.RTM.). Aclar.RTM. film is commonly used for high moisture barrier packaging in pharmaceutical applications.
2. Description of the Related Art
Blister packages are commonly formed by adhering a rigid, preformed plastic blister or product holding capsule to an underlying support of paperboard or the like, with the product confined between them. The plastic blister is generally formed from a clear, moldable material such as polyvinyl chloride (PVC). In order to get the plastic blister to adhere to the paperboard, an adhesive coating must be applied to the surface of the paperboard where the blister is attached. There are a number of extrudable adhesive resins available which will adhere to PVC, but not all are readily adhered to paperboard.
It is known in the art to use ethylene-methyl acrylate (EMA) as an adhesive coating for blister pack applications. EMA could be applied to paperboard using a conventional chill roll apparatus provided a chill roll release agent was used in the EMA. However, use of the chill roll release agent presented difficulty in getting the EMA to adhere to the paperboard. Removal of the chill roll release agent solved the product problem (adhesion of the EMA to the paperboard), but this created a production problem, i.e., adhesion of the EMA to the chill roll itself.
Finally, it is known to produce a blister pack laminate which is comprised of coextruding EMA with a polyolefin, preferably, a low density polyethylene (LDPE), which adheres to both paperboard and EMA, onto a paperboard substrate. The EMA contains a chill roll release agent to achieve good release from the chill roll, while the LDPE securely bonds the EMA to the uncoated surface of the paperboard despite the presence of the chill roll release agent.
Exemplary of such prior art is commonly assigned U.S. Pat. No. 5,091,261 ('261), to H. B. Casey et al., entitled "Paperboard/Polymer Laminate for Blister Pack". While the '261 patent has met with some degree of commercial success, the laminate in the '261 patent will not seal to Aclar.RTM.. Consequently, a more advantageous laminate, then would be presented if the laminate could seal to Aclar.RTM..
It is apparent from the above that there exists a need in the art for a paperboard laminate which can be employed in pharmaceutical blister packaging, but which at the same time is capable of being sealed to Aclar.RTM..
It is a purpose of this invention to fulfill this and other needs in the art in a manner more apparent to the skilled artisan once given the following disclosure.